I am not aware of any HDI-30/HDI-30 cables, and trying to kludge one from HDI-30/CN-50 cables at the same time as taking care of termination will tax chance, space and time all at once. I have a 2 x CN-50/DB-25 cable (such as is found at the input of Apple's external enclosures) from the eBay seller macmetex, but keep in mind that HDI-30 end connectors have to be the 30-pin rather than 29-pin kind to get the PB into zombie-mode.

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Sorry I don't know the correct denomination for those connectors. But I do have two of those "square PowerBook SCSI" to "normal Mac SCSI" adapters, one of which has a switch between "normal" and "zombie" modes. Hopefully you'll understand what I mean… 

Using those two adapters with a standard SCSI cable ("screw" connector at both ends) from a Iomega Zip drive, I have benn able to mount a zombie PowerBook on another PowerBook several times!